The invention concerns a measuring apparatus for measuring periodically varying forces and/or moments which occur on a rotating rotary member, for example unbalance effects or non-uniformities in respect of the rotary member which can be for example in the form of a pneumatic tire.
In measuring apparatuses for measuring unbalance phenomena on rotary bodies to be balanced or in testing machines for testing the uniformity of rotary members, for example pneumatic tires for motor vehicle wheels, the structure generally includes a machine bed which serves as a common supporting component for a measuring means for detecting the forces and/or moments involved, and the means for rotatably mounting the rotary member. The machine bed conventionally comprises a hollow box-like welded construction consisting of steel to which the mounting and fixing means for the components of the measuring means and rotary member mounting means are also welded.
In such measuring apparatuses, the measuring means for detecting the forces and/or moments include measurement value pick-up means or detectors which detect oscillations or vibrations due to the forces and/or moments in question. Besides the vibration which is due to unbalance or irregularity of the rotating rotary member, the vibrations detected by the measurement value pick-up means also include a number of other vibration components which have a disturbance effect and thus can falsify the measurement result. Those disturbing vibration components are transmitted to the measurement value pick-up assembly in particular from the outside of the apparatus structure, by way of the machine bed thereof. In addition, during a measuring run in which the rotary member to be tested and other components which rotate therewith are driven in rotation at a suitable speed, the rotary member and the components rotating therewith produce natural oscillations or vibrations of the machine bed, which are transmitted from there into the measurement value pick-up assembly.
As indicated above, in the above-discussed measuring apparatuses, the machine bed performs the function of a common supporting component for the measuring means and the means for mounting the rotary member. Nonetheless, the disadvantages of such an arrangement were accepted insofar as interference oscillations or vibrations were not prevented from being transmitted into the measurement value pick-up system so that interference vibrations or oscillations originating from outside the apparatus and also caused by natural vibration or oscillation of the machine bed were transmitted into or induced in the measurement value pick-up system.